Hydrogen Tunneling in Catalytic Hydrolysis and Alcoholysis of Silanes.

An unprecedented quantum tunneling effect has been observed in catalytic Si-H bond activations at room temperature. The cationic hydrido-silyl-iridium(III) complex, {Ir[SiMe(o-C6 H4 SMe)2 ](H)(PPh3 )(THF)}[BArF 4 ], has proven to be a highly efficient catalyst for the hydrolysis and the alcoholysis of organosilanes. When triethylsilane was used as a substrate, the system revealed the largest kinetic isotopic effect (KIESi-H/Si-D =346±4) ever reported for this type of reaction. This unexpectedly high KIE, measured at room temperature, together with the calculated Arrhenius preexponential factor ratio (AH /AD =0.0004) and difference in the observed activation energy [(E a D -E a H )=34.07 kJ mol-1 ] are consistent with the participation of quantum tunneling in the catalytic process. DFT calculations have been used to unravel the reaction pathway and identify the rate-determining step. Aditionally, isotopic effects were considered by different methods, and tunneling effects have been calculated to be crucial in the process.

Formation of Irida-ß-ketoimines and PCNamine-Ir(III) Complexes by Reacting Irida-ß-diketones with Aliphatic Diamines: Catalytic Activity in Hydrogen Release by Methanolysis of H3N-BH3.

Aliphatic diamines [(H2N(CH2)nNHR) (a-d) n = 2: R = H (a), R = CH3 (b), R = C2H5 (c), n = 3, R = H (d) or rac-2-(aminomethyl)piperidine (e)] react with [IrH(Cl){(PPh2(o-C6H4CO))2H}] in THF to afford ketoimine complexes [IrH(Cl){(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nNHR))H}] (2a-2d) or [IrH(Cl){(PPh2(o-C6H4CO))(PPh2(o-C6H4CNCH2(C5H9NH)))H}] (2e), containing a bridging N-H···O hydrogen bond and a dangling amine. Complex 2e consists of an almost equimolar mixture of two diastereomers. In protic solvents, the dangling amine in complexes 2 displaces chloride to afford cationic acyl-iminium compounds, [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH(CH2)nNHR))]X (3a-3d, X = Cl) or [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CNHCH2(C5H9NH)))]Cl (3e) and (4a-4b, X = ClO4), with new hemilabile terdentate PCNamine ligands adopting a facial disposition. Complexes 3 contain the corresponding phosphorus atom trans to hydride and the amine fragment trans to acyl, while complexes 4 contain the amine trans to hydride. 3b and 4b consist of 80:20 and 95:5 mixtures of diastereomers, respectively, while 3e contains a 65:35 mixture. In the presence of KOH, intermediate cationic acyl-iminium complexes 3 transform into neutral acyl-imine [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nNHR))] derivatives (5) with retention of the stereochemistry. Single-crystal X-ray diffraction analysis was performed on 2a, [3a]Cl, [3b]Cl, [4a]ClO4, and 5b. Complexes 2, 3, and 5 catalyze the methanolysis of ammonia-borane under air to release hydrogen. The highest activity is observed for ketoimine complexes 2.

(Diphenylphosphino)alkylaldehyde affords hydride- or alkyl-[(diphenylphosphino)alkylacyl]rhodium(iii) or (diphenylphosphino)alkylester complexes: theoretical and experimental diastereoselectivity.

The reaction of [RhCl(COD)]2 (COD = 1,5-cyclooctadiene) with racemic PPh2(CH(Ph)CH2CHO) and pyridine (py) led to the oxidative addition of the aldehyde, and a single geometric isomer of [RhHCl(PPh2(CH(Ph)CH2CO))(py)2] (1), with hydride trans to chloride, was obtained as a mixture of two diastereomers in a 95 : 5 ratio; this was in agreement with density functional theory (DFT) calculations. In a chloroform solution, the exchange of hydride by chloride yielded [RhCl2(PPh2(CH(Ph)CH2CO))(py)2] (2) as a mixture of a kinetically preferred species, trans-py-2a, and two diastereomers, cis-Cl-2b' and cis-Cl-2b, with cis pyridines and a chloride trans to acyl; as predicted by the DFT calculations, the latter was the major species. Complex 1 reacted with racemic PPh2(CH(Ph)CH2CHO) or PPh2(o-C6H4CHO) to afford [RhHCl(PPh2(CH(Ph)CH2CO))(κ1-PPh2(CH(Ph)CH2CHO))(py)] (3) or [RhHCl(PPh2(o-C6H4CO))(κ1-PPh2(CH(Ph)CH2CHO))(py)] (4), respectively, both with a dangling alkylaldehyde. Diastereomeric mixtures with the ratios 3a/3a' = 80 : 20 and 4a/4a' = 50 : 50 were obtained. Complex 4 reacted with N-donors to afford cationic [RhH(NN)(PPh2(o-C6H4CO))(κ1-PPh2(CH(Ph)CH2CHO))]BPh4 (NN = 1,10-phenanthroline, 5; 2,2'-bipyridine, 6) or with 8-aminoquinoline (aqui) or 2-(aminomethyl)pyridine to yield imination products with terdentate ligands: [RhH(PPh2(o-C6H4CO))(κ3-PNN)]BF4 (PNN = PPh2(CH(Ph)CH2CNC9H6N), 7 and PPh2(CH(Ph)CH2CNCH2C5H4N), 8, respectively. Compounds 5-8 were obtained as equimolar a/a' mixtures of diastereomers. Moreover, 5a and 5a' could be separated. [RhCl(NBD)]2 reacted with racemic PPh2(CH(Ph)CH2CHO) and N-donors to provide nortricyclyl (Ntyl) derivatives [RhCl(NN)(Ntyl)(PPh2CH(Ph)CH2CO)] (NN = phen, 9 and bipy, 10) as an a/a' = 75 : 25 mixture of diastereomers. By reacting [RhCl(NBD)]2 with PPh2(CH(Ph)CH2CHO) and quinoline-8-carbaldehyde in methanol, the phosphino-ester complex [RhCl(Ntyl)(C9H6NCO)(κ2-PPh2CH(Ph)CH2CO(OCH3)] 11 was obtained. The initial equimolar mixture of two diastereomers readily transformed into a single diastereomer, which was found to be thermodynamically most stable by the DFT calculations. Furthermore, single crystal X-ray diffraction analysis of cis-Cl-2b, 5a, 7a, 10a and 11 is reported.

Secondary Oxide Phosphines to Promote Tandem Acyl-Alkyl Coupling/Hydrogen Transfer to Afford (Hydroxyalkyl)rhodium Complexes. Theoretical and Experimental Studies.

Acyl(σ-norbornenyl)rhodium(III) dimer [Rh(µ-Cl)(C9H6NCO)(C7H9)L]2 (1) (C7H9 = σ-norbornenyl; L = 4-picoline, isoquinoline) reacts with diphenylphosphine oxide (SPO) to undergo a one-pot reaction involving (i) cleavage of the chloride bridges and coordination of the phosphine, (ii) C-C bond coupling between acyl and norbornenyl in a 18e species, and (iii) ligand-assisted outer-sphere O(P)-to-O(C) hydrogen transfer, to afford mononuclear 16e species [RhCl{(C9H6NC(O)C7H9)(Ph2PO)H}(L)] (2) containing a quinolinyl-(norbornenylhydroxyalkyl) fragment hydrogen-bonded to a κ1- P-phosphinite ligand. Pentacoordinated 2, which adopt a distorted trigonal bipyramidal structure, are kinetic reaction products that transform into the thermodynamic favored isomers 3. Structures 3 contain an unusual weak η1-C anagostic interaction involving the rhodium atom and one carbon atom of the olefinic C-H bond of the norbornenyl substituent in the chelating quinolinyl-hydroxyalkyl moiety. Their structure can be described as pseudoctahedral, through a 5 + 1 coordination, with the anagostic interaction in a trans disposition with respect to the phosphorus atom of the phosphinite ligand. Complexes were characterized in solution by NMR spectroscopy and electrospray ionization mass spectrometry. Complex [RhCl{(C9H6NC(O)C7H9)(Ph2PO)H}(4-picoline)] (3a) was also identified by X-ray diffraction. Density functional theory calculations confirm the proposed structures by a plausible set of mechanisms that accounts for the 1 (monomer) → 2 → 3 transformation. Lowest-energy pathways involve reductive elimination of quinolinylnorbornenylketone, still coordinated in the rhodium(I) species thus formed, followed by O-to-O hydrogen transfer from κ1- P-SPO to the sp3 hybridized carbonyl group (formal alkoxide) avoiding the otherwise expected classical release of ketone. Theoretical 13C NMR studies also confirm the experimental spectral data for the considered structures.

Irida-ß-ketoimines Derived from Hydrazines To Afford Metallapyrazoles or N-N Bond Cleavage: A Missing Metallacycle Disclosed by a Theoretical and Experimental Study.

Unprecedented metallapyrazoles [IrH2{Ph2P(o-C6H4)CNNHC(o-C6H4)PPh2}] (3) and [IrHCl{Ph2P(o-C6H4)CNNHC(o-C6H4)PPh2}] (4) were obtained by the reaction of the irida-ß-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNNH2))H}] (2) in MeOH heated at reflux in the presence and absence of KOH, respectively. In solution, iridapyrazole 3 undergoes a dynamic process due to prototropic tautomerism with an experimental barrier for the exchange of ΔGcoal⧧ = 53.7 kJ mol-1. DFT calculations agreed with an intrapyrazole proton transfer process assisted by two water molecules (ΔG = 63.1 kJ mol-1). An X-ray diffraction study on 4 indicated electron delocalization in the iridapyrazole ring. The reaction of the irida-ß-diketone [IrHCl{(PPh2(o-C6H4CO))2H}] (1) with H2NNRR' in aprotic solvents gave irida-ß-ketoimines [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNNRR'))H}] (R = R' = Me (5); R = H, R' = Ph (8)), which can undergo N-N bond cleavage to afford the acyl-amide complex [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4C(O)N(CH3)2))-κP,κO] (6) or [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4CN)-κP)(NH2NHPh-κNH2)] (9) containing o-(diphenylphosphine)benzonitrile and phenylhydrazine, respectively. From a CH2Cl2/CH3OH solution of 9 kept at -18 °C, single crystals of [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4CN)-κP))(HN═NPh-κNH)] (10) containing o-(diphenylphosphine)benzonitrile and phenyldiazene were formed, as shown by X-ray diffraction. The reaction of 1 with methylhydrazine in methanol gave the hydrazine complex [IrCl(PPh2(o-C6H4CO))2(NH2NH(CH3)-κNH2)] (7). Single-crystal X-ray diffraction analysis was performed on 6 and 7.

Stereoselective formation and catalytic activity of hydrido(acylphosphane)(chlorido)(pyrazole)rhodium(III) complexes. Experimental and DFT studies.

The reaction of [{RhCl(COD)}2] (COD = 1,5-cyclooctadiene) with L = pyrazole (Hpz), 3(5)-methylpyrazole (Hmpz) or 3,5-dimethylpyrazole (Hdmpz) and PPh2(o-C6H4CHO) (Rh : L : P = 1 : 2 : 1) gives hydridoacyl complexes [RhHCl{PPh2(o-C6H4CO)}(L)2] (). Stereoselective formation of and with pyrazoles trans to hydrido and phosphorus and hydrogen bond formation with O-acyl and chlorido occur. is a mixture of two linkage isomers in a 9 : 1 ratio, with two 5-methylpyrazole ligands or with one 3- and one 5-methylpyrazole ligand, respectively. Fluxional undergoes metallotropic tautomerization and is a mixture of equal amounts of and , with hydrido trans to pyrazole or chlorido, respectively. Complexes readily exchange hydrido by chlorido to afford [RhCl2{PPh2(o-C6H4CO)}(L)2] (, and ) as single isomers with cis chloridos and two N-HCl hydrogen bonds. The reaction of with PPh3 or PPh2OH affords static [RhHCl{PPh2(o-C6H4CO)}(PPh3)L] () or [RhHCl{PPh2(o-C6H4CO)}(PPh2OH)L] () respectively with trans P-atoms and pyrazoles forming N-HCl hydrogen bonds. and contain single species with hydrido cis to chlorido, while is a mixture of equal amounts of and . Complexes , with an additional O-HO hydrogen bond, selectively contain only the cis-H,Cl species with all the three ligands. The reaction of [{RhCl(COD)}2] with L and PPh2(o-C6H4CHO) (Rh : L : P = 1 : 1 : 2) led to complexes with trans P-atoms, [RhHCl{PPh2(o-C6H4CO)}{PPh2(o-C6H4CHO)-κP}L] (, and ), at room temperature, and to [RhCl{PPh2(o-C6H4CO)}{PPh2(o-C6H4CHOH)}(Hmpz)] () or [RhCl{PPh2(o-C6H4CO)}2L] () with hydrogen evolution in refluxing benzene. DFT calculations were used to predict the correct isomers, their ratios and the particular intramolecular hydrogen bonds in these complexes. Single crystal X-ray diffraction analysis was performed on , and . Complexes are efficient homogeneous catalysts (0.5 mol% loading) in the hydrolysis of amine- or ammonia-borane (AB) to generate up to 3 equivalents of hydrogen in the presence of air.

A readily accessible ruthenium catalyst for the solvolytic dehydrogenation of amine-borane adducts.

The use of the readily available complex [Ru(p-Cym)(bipy)Cl]Cl as an efficient and robust precatalyst for homogeneously catalysed solvolysis of amine-borane adducts to liberate the hydrogen content of the borane almost quantitatively is being presented. The reactions can be carried out in tap water, and in aqueous mixtures with non-deoxygenated solvents. The system is also efficient for the dehydrocoupling of dimethylamine-borane under solvent-free conditions.

Efficient hydridoirida-ß-diketone-catalyzed hydrolysis of ammonia- or amine-boranes for hydrogen generation in air.

The dihydridoirida-ß-diketone [IrH2{(PPh2(o-C6H4CO))2H}] (2) has been used as a homogeneous catalyst for the hydrolysis of ammonia- or amine-boranes to generate up to 3 equivalents of hydrogen in the presence of air. When using 0.5 mol% loading of 2, dimethylamine-borane is hydrolysed completely within 8 min at 30 °C and maintains its activity in consecutive runs. Ammonia-borane or tert-butylamine-borane is hydrolysed completely within 32 or 25 min respectively. Triethylamine-borane fails to be hydrolysed. Kinetic studies suggest a sequence of two consecutive first-order reactions, in which an intermediate builds up and finally falls, with the first step being the rate controlling step. ΔH1(‡) are in the range 65-85 kJ mol(-1) and negative values of ΔS1(‡) are obtained. A multinuclear NMR study of the catalyzed reaction shows the formation of a resting state (A) of the active catalyst proposed to be of the hydridodiacyl type [IrH(PPh2(o-C6H4CO))2(solvent)] with a hydride trans to the acyl group. In the absence of substrate a dormant species (B) is formed. By the reaction of hydridoirida-ß-diketones with ammonia, the hydridoirida-ß-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH))H}] (3) and the hydridobis(acylphosphane)aminoiridium(III) complex [IrH(PPh2(o-C6H4CO))2(NH3)] (4), with a hydride trans to phosphane, are formed. Aromatic amines such as aniline or anisidines afford cationic [IrH{(PPh2(o-C6H4CO))2H}(C6H4RNH2)]ClO4 (R = H (6); p-MeO (7); o-MeO (8)) hydridoirida-ß-diketones with a coordinated amine group trans to the hydride. The dormant species B is proposed to be of the hydridobis(acylphosphine)aminoiridium(III) type with a hydride trans to the amine group.

Reactions of hydridoirida-ß-diketones with amines or with 2-aminopyridines: formation of hydridoirida-ß-ketoimines, PCN terdentate ligands, and acyl decarbonylation.

The hydridoirida-ß-diketone [IrHCl{(PPh(2)(o-C(6)H(4)CO))(2)H}] (1) reacts with benzylamine (C(6)H(5)CH(2)NH(2)) to give the hydridoirida-ß-ketoimine [IrHCl{(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNCH(2)C(6)H(5)))H}] (2), stabilized by an intramolecular hydrogen bond. 2 reacts with water to undergo hydrolysis and amine coordination giving hydridodiacylamino [IrH(PPh(2)(o-C(6)H(4)CO))(2)(C(6)H(5)CH(2)NH(2))] (3). Cyclohexylamine or dimethylamine lead to hydridodiacylamino [IrH(PPh(2)(o-C(6)H(4)CO))(2)L] (4-5). In chlorinated solvents hydridodiacylamino complexes undergo exchange of hydride by chloride to afford [IrCl(PPh(2)(o-C(6)H(4)CO))(2)L] (6-9). The reaction of 1 with hydrazine (H(2)NNH(2)) gives hydridoirida-ß-ketoimine [IrHCl{(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNNH(2)))H}] (10), fluxional in solution with values for ΔH(‡) of 2.5 ± 0.3 kcal mol(-1) and for ΔS(‡) of -32.9 ± 3 eu. A hydrolysis/imination sequence can be responsible for fluxionality. 2-Aminopyridines (RHNC(5)H(3)R'N) react with 1 to afford cis-[IrCl(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CHNRC(5)H(3)R'N))] (R = R' = H (11), R = CH(3), R' = H (12), R = H, R' = CH(3) (13)) containing new terdentate PCN ligands in a facial disposition and cis phosphorus atoms as kinetic products. The formation of 11-13 requires imination of the hydroxycarbene moiety of 1, coordination of the nitrogen atom of pyridine to iridium, and iridium to carbon hydrogen transfer. In refluxing methanol, complexes 11-13 isomerize to afford the thermodynamic products 14-16 with trans phosphorus atoms. Chloride abstraction from complexes [IrCl(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CHNRC(5)H(4)N))] (R = H or CH(3)) leads to decarbonylation of the acylphosphine chelating group to afford cationic complexes [Ir(CO)(PPh(2)(o-C(6)H(4)))(PPh(2)(o-C(6)H(4)CHNRC(5)H(4)N))]A, 17 (R = H, A = ClO(4)) and 18 (R = CH(3), A = BF(4)) as a cis/trans = 4:1 mixture of isomers. Single crystal X-ray diffraction analysis was performed on 6, 9, 13, and 14.

A hydridoirida-beta-diketone as an efficient and robust homogeneous catalyst for the hydrolysis of ammonia-borane or amine-borane adducts in air to produce hydrogen.

The first homogeneous metal-catalysed hydrolysis of ammonia-borane or amine-borane adducts for hydrogen generation, using a stable organometallic complex [IrHCl{(PPh(2)(o-C(6)H(4)CO))(2)H}], is reported.

Selective formation of cis-diacyl, cis-PPh(2)R rhodium(III) complexes by the reaction of rhodium(III) cis-diacyl, trans-PPh(2)R complexes with aliphatic diamines.

The cis-diacyl, trans-PPh(2)R complex [RhCl(PPh(2)(o-C(6)H(4)CO))(2)(pyridine)] () reacts with substituted aliphatic diamines to afford selectively cationic cis-diacyl, cis-PPh(2)R, diamine derivatives [Rh(PPh(2)(o-C(6)H(4)CO))(2)(NN')](+) (NN' = 1,2-diphenylethylenediamine, 2; 1,2-propanediamine, 3; N-methylethylenediamine, 4; N,N-dimethylethylenediamine, 5; N,N'-dimethylethylenediamine, 6; N,N,N'-trimethylethylenediamine, 7) with high stereoselectivity depending on the N-donor ligand employed. Complexes 2 and 3 contain a single isomer, while 4 is a mixture of two isomers, 4a and 4b. Formation of 4a occurs first and is followed by isomerisation to 4b until the equilibrium 4a:4b = 1:4 ratio is attained. In contrast, 5 and 6 contain a single isomer. More basic amino groups prefer positions trans to an acyl group while less basic amino groups are trans to a phosphine group. The preferred intramolecular N-H...O hydrogen bond formation between an amino and an acyl coordinated ligands, trans to the phosphorus atoms, appears to be relevant to the selectivity observed. 7 is a mixture of two isomers 7a and 7b in a 7a:7b = 5.7:1 ratio. N,N,N',N'-tetramethylethylenediamine or N,N'-diphenylethylenediamine led to the elimination of the N-donor ligands and the formation of a mixture of isomers of [Rh(2)(mu-Cl)(mu-PPh(2)(o-C(6)H(4)CO))(2)(PPh(2)(o-C(6)H(4)CO))(2)](+) (), where the Rh atoms are triply bridged by two acyl groups in a head-to-tail arrangement and by a chloride. The reaction of [Rh(PPh(2)(o-C(6)H(4)CO))(2)(ndmeen)]ClO(4) (5) with acids led to the displacement of the diamine and the formation of a [8a](+):[8b](+):[8c](+) = 1:1:3 mixture. 8c, containing the weakest sigma-donor oxygen atoms trans to the strongest sigma-donor acyl groups, represents the most electronically favourable geometry for . All the complexes were fully characterized spectroscopically. Single crystal X-ray diffraction analysis was performed on 5, 6, 8a and 8b.

Aldehyde C-H activation with late transition metal organometallic compounds. Formation and reactivity of acyl hydrido complexes.

This perspective focuses on the aldehyde C-H activation promoted by late transition metals, including the chelation-assisted reactions. The mechanisms currently accepted for different metal complexes, the reactivity of acyl hydrido species formed, and the reactions promoted on further aldehyde when using excess reagent are discussed. Homogeneous catalytic aldehyde decarbonylation or dimerization reactions are also reviewed.

New hydridoirida-beta-diketones derived from 8-quinoline-carbaldehyde and o-(diphenylphosphino)benzaldehyde.

8-Quinoline-carbaldehyde (C(9)H(6)NCHO) reacts in methanol with [IrCl(Cod)](2) (Cod = 1,5-cyclooctadiene) to give the acylhydrido complex [IrHCl(C(9)H(6)NCO)(Cod)] (1) or with [IrHCl{PPh(2)(o-C(6)H(4)CO)}(Cod)] to afford the hydridoirida-beta-diketone complex [IrHCl({PPh(2)(o-C(6)H(4)CO)}(C(9)H(6)NCO)H)] (2). Complex 2 reacts with silver perchlorate in the presence of pyridine to afford the cationic [IrH({PPh(2)(o-C(6)H(4)CO)}(C(9)H(6)NCO)H)(py)]ClO(4) (), which in solution transforms slowly into the cationic dinuclear complex [Ir{micro-PPh(2)(o-C(6)H(4)CO)}(C(9)H(6)NCO)(py)](2)(ClO(4))(2) (4) with two acylphosphine chelate-bridging ligands. The reaction of 2 with AgClO(4) in the presence of carbon monoxide affords [IrH({PPh(2)(o-C(6)H(4)CO)}(C(9)H(6)NCO)H)(CO)]ClO(4) (5), which in solution is in equilibrium with the deprotonated diacylhydrido complex [IrH{PPh(2)(o-C(6)H(4)CO)}(C(9)H(6)NCO)(CO)] (6). The reaction of 2 with Et(3)OPF(6) results in the formation of [[IrH({PPh(2)(o-C(6)H(4)CO)}(C(9)H(6)NCO)H)](2)(micro-Cl)]PF(6) (7), containing a cationic dinuclear species with a single chlorine atom bridging two hydridoirida-beta-diketone fragments. The reaction of with [Rh(OMe)(Cod)](2) affords the hydridoirida-beta-diketonaterhodium(I) complex [IrHCl{micro-PPh(2)(o-C(6)H(4)CO)}(micro-C(9)H(6)NCO)Rh(Cod)] (8), which isomerizes to the thermodynamically stable isomer [IrCl{PPh(2)(o-C(6)H(4)CO)}(micro-H)(micro-C(9)H(6)NCO)Rh(Cod)] (9). The catalytic activity of these complexes in the hydrogen transfer from isopropanol to cyclohexanone has been tested. The X-ray diffraction structures of complexes 2, 4 and 9 are reported.

Reactivity of hydridoirida-beta-diketones with bases: the selective formation of new di-mu-acyl-mu-hydridodiiridium(III) or dihydridoirida-beta-diketone complexes and heterometallic Ir(III)-Rh(I) derivatives.

The hydridoirida-beta-diketone [IrHCl{(PPh2(o-C6H4CO))2H}] (1a) reacts with bases such as KOH or NaHCO3 in methanol to undergo dehydrodechlorination and acyl-bridge formation affording [Ir2H2(PPh2(o-C6H4CO))2(mu-PPh2(o-C6H4CO))2] (2) with two acylphosphine chelate-bridging ligands, in a head-to-tail disposition, and terminal hydrides. The acyl bridges can be broken by pyridine, PPh3, CO or dimethylsulfoxide affording selectively mononuclear diacylhydrido neutral derivatives [IrH(PPh2(o-C6H4CO))2L] (3-6). la reacts with KOH or NaHCO3 in refluxing methanol to afford a novel dihydridoirida-beta-diketone [IrH2{(PPh2(o-C6H4CO))2H}](7), via dehydrodechlorination to afford 2, which then undergoes hydrogenation and protonation. The reaction of la with NEt3 affords 2 and [NHEt3]Cl. Further reaction affords [Ir2(mu-H){mu-PPh2(o-C6H4CO)}2(PPh2(o-C6H4CO))2] (8), with two acylphosphine chelate-bridging ligands and a bridging hydride. Neutral or cationic hydridoirida-beta-diketone complexes react with [Rh(cod)(OMe)]2 (cod = 1,5-cyclooctadiene) to afford hydridoirida-P-diketonaterhodium(I) complexes [IrHCl(mu-PPh2(o-C6H4CO))2Rh(cod)] (9) or [IrHL(mu-PPh2(o-C6H4CO))2Rh(cod)]ClO4 (L = py, 10; CO, 11), respectively that isomerise to the thermodynamically stable isomers of [IrCl(PPh2(o-C6H4CO))(mu-H))(mu-PPh,2(o-C6H4CO))Rh(cod)] (12) or [Ir(py)(PPh2(o-C6H4CO))(mu-H))(mu-PPh2(o-C6H4CO))Rh(cod)]ClO4(13). The reaction of 7 with [Rh(cod)(OMe)]2 affords [Ir(PPh2(o-C6H4CO))2(mu-H)2Rh(cod)](14). All the complexes were fully characterised spectroscopically. Single-crystal X-ray diffraction analysis was performed on 2, 4, 7, [8]ClO4 and 9.

Novel hydridoirida-beta-diketones containing small molecules, CO, or ethylene: their behavior in coordinating solvents such as dimethylsulfoxide or acetonitrile.

New hydridoirida-beta-diketones [IrH[(PPh2(o-C6H4CO))2H](CO)]ClO4 2 and [IrH[(PPh2(o-C6H4CO))2H](olefin)]BF4 (olefin = C2H4, 5; 1-hexene, 10) have been prepared. These complexes may afford new diacylhydridoiridium(III) derivatives. In chloroform solution, complex 2 is in equilibrium with the deprotonated diacylhydride trans-[IrH(PPh2(o-C6H4CO))2(CO)] complex 3. In DMSO, deprotonation of 2 occurs to yield the kinetically favored product 3, which isomerizes to the thermodynamically favored complex cis-[IrH(PPh2(o-C6H4CO))2(CO)] 4. Reprotonation of 4 with HBF4 in chlorinated solvents gives the cation in 2. In coordinating solvents such as dimethyl sulfoxide or acetonitrile, complex 5 undergoes displacement of ethylene to afford [IrH{(PPh2(o-C6H4CO))2H](L)]BF4 (L = DMSO, 7; CH3CN, 9). Complexes 5 and 7 undergo deprotonation by NEt3 to give the corresponding diacylhydrides. The ethylene complex gives only trans-[IrH(PPh2(o-C6H4CO))2(C2H4)] 6, while the dimethyl sulfoxide derivative affords a mixture of trans- and cis-[IrH(PPh2(o-C6H4CO))2(DMSO)] 8. Complex 10 shows inhibited alkene rotation around the Ir-olefin axis. All of the complexes were fully characterized spectroscopically. Single-crystal X-ray diffraction analysis was performed on complexes 3, 4, and 9. The 13C NMR and X-ray data point to a carbenoid character in the carbon atoms bonded to iridium in the irida--diketone fragment, so that it can be considered as an acyl(hydroxycarbene) moiety.